1. Field of the Invention
The present invention relates to a seek routine in a hard disk drive.
2. Background Information
Hard disk drives contain a plurality of magnetic heads that are coupled to rotating disks. The heads can magnetize and sense the magnetic fields of the disks to write and read data, respectively. The heads each have an air bearing surface that cooperates with a flow of air generated by the rotating disk to create an air bearing. The air bearing prevents mechanical wear between the head and the disk.
The data is typically stored on annular tracks that extend radially across each disk surface. To access data in different tracks the drive moves the heads across the disk surfaces in accordance with a seek routine. The seek routine is typically performed in accordance with a program performed by the controller of the disk drive.
The surface of the disk may have protrusions caused by disk defects or contaminants embedded into the disk surface. Impact between the head and the protrusion may create heat that degrades the read back signal. This phenomenon is sometimes referred to as a thermal asperity. Additionally, impact may create instability in the air bearing and cause an erroneous reading or writing of data. For this reason most disk drives identify such protrusions and avoid reading or writing in the protruded areas.
During a seek routine the heads are moved across the disk surfaces without regard to whether a protrusion(s) is in the seek path. Impact or multiple impacts with a protrusion during a seek routine could scratch the head or disk. The scratch could be extended over a larger area of the disk if a particle is dragged across the disk surface by the head. Additionally, impact can also produce head instability and cause an erroneous reading or writing of data. It would be desirable to provide a seek routine that avoids protrusions in the disk surfaces.